All four were located between the Russian Empire in the east and the French Third Republic and the United Kingdom in the west. The alliances made between these four nations were a result of Germany's inability to gain power on the "world stage". The Germans then decided to focus on creating an alliance of Mitteleuropa, i.e., Central Europe. The Balkans were originally desired as members of this alliance, but as the Balkans formed separate, autonomous states this was deemed impossible.

Italy

On 7 October 1879, Germany and Austria-Hungary became allies and formed the Dual Alliance. On 20 May 1882, they were joined by the Kingdom of Italy in what was known as the Triple Alliance. This alliance was intended to be limited to defensive purposes only.[2][3]

When World War I began, the petition made by Germany and Austria-Hungary for Italian intervention was rejected by the Italian Government on the grounds of these two countries declaring war on the Kingdom of Serbia, rather than taking defensive action against it.

Italy eventually entered World War I on May 23, 1915, but it fought against Germany and Austria-Hungary rather than with them, because of the land promised them in the Treaty of London made with France and Britain. This treaty promised Italy the Italian lands of the Habsburg Empire and territories in Asia Minor, Africa and the Balkans.[4]

Ottoman Empire joins

Following the outbreak of war in Europe during August 1914, the Ottoman Empire intervened at the end of October by taking action against Russia, resulting in declarations of war by the Triple Entente.

Bulgaria joins

Bulgaria, still resentful after its defeat in July 1913 at the hands of Serbia, Greece, Romania and the Ottoman Empire, was the last nation to enter the war against the Entente, invading Serbia in conjunction with German and Austro-Hungarian forces in October 1915.